Saturday, August 30, 2008

Testing .22 ammunition for velocity and accuracy. Lessons learned?

I've been building up to this range test for a few weeks now. Tweaking the rifle and gathering rim fire ammunition to squander.

I had two goals, besides the obvious one of spending a day trying to wear out the Marlins barrel. I wanted a look at the velocity numbers of various makes of .22 ammo, and I wanted to pin down what the Marlin shoots best.

As a side bar, I was very curious if velocity consistency is a key to rim fire accuracy, as it is in a center fire. With my heavy barrel varmint rifle I look for less than 20 fps variation shot to shot. This tells me I have a load with consistent internal ballistics. I expect the same from any match ammunition I load, including pistol rounds.

My plan for the days testing was to fire a twenty round string of each cartridge. All from the same rifle, same targets, same bench, same shooter, etc. Fired into four groups of five rounds each, this should provide a rough but fair result in the search for the most accurate (as far as this Marlin is concerned, anyway).

Shooting every round over my chronograph and recording the data, I would then have a decent record of each brands average velocity and it's variations. I wasn't sure what the data would show, but it would be interesting to see the results and chart them.

The shooting day started at 9am for me, and abruptly came to a temporary stop at 9:05. A nest of yellow jackets had adopted the fifty yard back stop I chose, and my initial setup target was their new God.

I had planned to attach a dozen targets to a sheet of cardboard, cutting out some down time spent hanging paper. The Cardboard had a target on it I use to set up and align the chrono. For some reason the little wasps thought this target was the most fascinating thing ever seen, and swarmed it. Hovering by the hundreds in front of it, worshiping like Obamaites at the convention.

Four partial cans of wasp spray only thinned them out a little, so I came to an agreement with the little buggers. I left them the target they loved so much, and I hung mine a few feet over to the right. The separation agreement worked well for all concerned. I proceeded to fire a dozen foulers, and set up the alignment of the chronograph. The rest of the day I co-existed with the yellow jackets in a strange form of shooty peace. Each time I looked through the spotting scope, I could see mounds of little wasps crawling over the large target. The smaller targets I was shooting for record they completely ignored.

Each target was numbered, for a total of sixteen targets. The numbers matched those at the top of data sheets I had preprinted and arranged in a binder. Each page was used to record the make and model of the cartridge, along with all the velocity data collected. The speed of each round fired was noted, along with average velocity, highs and lows, extreme spread, standard deviation, and average deviation for the string.

Accuracy was measured hours after the shoot, looking only at the numbered targets in the binder. Groups were checked and averaged without knowing what cartridge was mated to which target. The target data was then transferred to the cartridge data sheets for comparison. This round-about method helped me leave my own ammunition prejudices aside as I looked for results.

In this first chart (click to enlarge for easier reading), I have listed each type tested, it's average velocity, extreme velocity spread, and average group size.

At first blush, the results would seem pretty confusing. The ammunition with the best accuracy did not always have the least velocity variations. The question remains in my mind... how much of the data is flawed simply because I needed to concentrate more....to shoot better?

Anecdotal evidence suggests this may be a significant factor. Many of the targets showed four shots touching, then a flier an inch away. The velocity numbers don't always explain the fliers.

Some targets were clear, with large groups dispersed evenly around the bullseye. Others showed excellent promise for tight groups, till a blasted flier opened it up. Fliers are always a question..... was it the ammunition or the shooter?

The data showed that wide velocity variations were not solely the realm of cheap ammunition. While Federal bulk pack had a huge spread, so did some very expensive RWS subsonic.In addition, accuracy seemed to be dependent on velocity numbers to only a small degree. Far more important were bullet weight and style. The ammunition loaded with lighter bullets of a more conical shape shot the worst from this Marlin 780. CCI Quik-Shok stood out from the crowd in that manner, with very high velocity bullets fired into groups so large their was no reason to measure them. The Marlin clearly despised the Quik-Shok round.

Most impressive, velocity and accuracy wise, were the relatively expensive match rounds. Both the Eley and the Fiocchi shot a few astounding groups and both had the lowest velocity variations of the pack. Where the Federal bulk pack made consistently large groups, the Eley would land four rounds in one wide hole, then another hole half an inch off the groups center.On the other hand, at $70 a brick (500 rounds), I won't be rushing out to buy a case of Eley anytime soon.

In the range of reasonably priced ammunition, both the PMC Sidewinders and the Federal Champion 510 ammunition built promising groups without wild velocity variations, although 80+ fps is still a pretty wide spread. CCI Subsonic hollow points did the same.

What did I learn, after firing sixteen different rounds with serious intent? Clearly I can go buy a few bricks of Federal Champion and have a reasonable expectation it will perform decently in this Marlin. CCI Subsonics will make an excellent small game round for the rifle as well. Past that.....The Match ammunition? For what it costs, I think I'll pass. I'm not doing any shooting with this rifle that demands that kind of potential, especially at the price. 0.75" - 0.80" groups at fifty yards make this a fine squirrel rifle, and at $2.80 a box for the Federal I can shoot as much as I like.

I had planned to test half a dozen types of .22 short as well, but their accuracy was so poor from the Marlin that it became pointless. CCI CB Long was also tested, but its such a different animal that it doesn't belong in this mix at all.

One fact I did come away with... every rifle is very different. Replacing the Marlin 780 on the bench with my new CZ452, it was a different ball game. The Eley that had 40 fps variations in the Marlin had only a 13 fps spread in the CZ. The Federal bulk that had so-so accuracy in the Marlin grouped exceptionally well in the CZ. The longer barrel on the CZ resulted in lower velocities as well.I would have enjoyed being able to announce "This .22 Ammunition is the best! Your rifle will love it and you will be pleased!". But.... I can't do that. Each rifle is different, especially in rim fire. The only conclusions I can draw are the obvious ones..... each shooter will have to run these tests (at least the accuracy portion) for them self, with each different rim fire rifle they are interested in.On the other hand.... that just means a lot of shooting. How bad can that be?

Excellent post with some interesting results! I'm not surprised at the small variations in the target ammo, but I am surprised at the spreads you encountered. And as you said, the key point is what the rifle likes!\Thanks for the update!

Great informative post. I am very impressed with the degree of care you took to make things as accurate as possible. You barrel modification in and of itself was something I had never even thought or heard of.

After competing in a postal match last winter with my Marlin 39, I came to the same conclusions you did, except I had no verification of bullet speeds and used 6 or so different brands of ammo. The Dynamit Noble Target ammo ended up being the best of the bunch for that 39a, the surprise was that Remington 550 bulk pack was right on par with it. Just goes to show that expensive ammo, won't always get you the best accuracy. Thanks for the detailed results of your test. It is interesting to see the variance of bullet speeds within the same brand lots.